在openlayers中制作危险源标识可以需要动态扩散的点（有很多种方法 可以加入jpg动图，也可以写css动画） 这里提供一种思路用openlayer自带的方法写 并给予详细的方法注释供初学者学习 （所有jar包都是在线的代码可以复制过去直接用）
<!DOCTYPE html>
<html>
<head>
<title>Icon Symbolizer</title>
<link rel="stylesheet" href="https://openlayers.org/en/v3.20.1/css/ol.css" rel="external nofollow" type="text/css">
<script src="https://cdn.polyfill.io/v2/polyfill.min.js?features=requestAnimationFrame,Element.prototype.classList,URL"></script>
<script src="https://openlayers.org/en/v3.20.1/build/ol.js"></script>
<script src="https://code.jquery.com/jquery-2.2.3.min.js"></script>
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.min.css" rel="external nofollow" >
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/js/bootstrap.min.js"></script>
<style>
#map {
position: relative;
}
#popup {
cursor: pointer;
}
</style>
</head>
<body>
<div id="map" class="map"></div>
<div id="styleType">
</div>
<script>
//水纹扩散
var bingMap = new ol.layer.Tile({
source :new ol.source.XYZ({
crossOrigin: 'anonymous',
url:'http://www.google.cn/maps/vt?lyrs=m@189&gl=cn&x={x}&y={y}&z={z}'
})
});
var map = new ol.Map({
layers: [bingMap],
target: 'map',
view: new ol.View({
center: ol.proj.transform([112.91, 28.21], 'EPSG:4326', 'EPSG:3857'),
zoom: 5
})
});
var source = new ol.source.Vector({
wrapX: false
});
var vector = new ol.layer.Vector({
source: source
});
map.addLayer(vector);
function addRandomFeature() {
var geom = new ol.geom.Point(ol.proj.fromLonLat([112.91, 28.21]));
var feature = new ol.Feature(geom);
source.addFeature(feature);
}
var duration = 1000;
function flash(feature) {
var start = new Date().getTime();
//进行地图水波渲染
var listenerKey = map.on('postcompose', animate);
function animate(event) {
//获取几何图形
var vectorContext = event.vectorContext;
//获取当前渲染帧状态
var frameState = event.frameState;
//添加一个OpenLayers.Geometry几何对象
var flashGeom = feature.getGeometry().clone();
//渲染帧状已占时间
var elapsed = frameState.time - start;
//已占比率
var elapsedRatio = elapsed / duration;
// radius半径为5结束为30
var radius = ol.easing.easeOut(elapsedRatio) * 25 + 5;
//不透渐变消失
var opacity = ol.easing.easeOut(1 - elapsedRatio);
//Circle样式
var style = new ol.style.Style({
image: new ol.style.Circle({
radius: radius,
stroke: new ol.style.Stroke({
color: 'rgba(255, 0, 0, ' + opacity + ')',
width: 1 + opacity
})
})
});
//给几何图形添加样式
vectorContext.setStyle(style);
//将几何体渲染到画布中
vectorContext.drawGeometry(flashGeom);
if (elapsed > duration) {
start = frameState.time ;
;
}
//请求地图渲染（在下一个动画帧处）
map.render();
}
}
//数据源添加图层
source.on('addfeature', function(e) {
flash(e.feature);
});
addRandomFeature()
</script>
</body>
</html>
